Wheel alignment gauge



y 1952 H. o. HOLADAY 2,603,881

WHEEL ALIGNMENT GAUGE Filed May 20, 1947 2 SHEETSSHEET 1 Q INVENTOR.

fifarala 0720 laa'ay B: BY

y 1952 H. o. HOLADAY 2,603,881

WHEEL ALIGNMENT GAUGE Filed May 20. 1947 2 SHEETS-SHEET 2 k/ V I W V Y 55 mmvnm jqrold a fi/azada Patented July 22, 1952 PAT T Y This invention relates to improvements in Wheel alignment gauges, and refers specifically to,..a gauge 'formeasuring the alignment angles of the front wheels gran auto1nobi1e,,;the gauge bein characterized thatith'e angular alignment measurements are-indicatedelectrically; I

I One of the, objects the} ,present linvention resides inthe provision ofimechanis m for quickly and convenientiyindicating the-magnitude of the alignment angles .oi the mm wheels of La motor v hicle.) i, i Another object lot ;the inventioniesides. in means for quickly and conveniently adjustingthe measuring device to" a datum tori zero position preparatory to, or during, the measuring of said alignmentangles A iurther object of fi c ployment oft-an electricalLbridgecircuit Whereby'loy the use of ipropger constahtathe ratiomuse:

rearrange may e 1 igned any des'ired 1 r asc iracy, Other objects and,.' a dvantages ,ojf th e"- pr jasent invention will be apparent from thejiacoomnany ing drawing and following vdetaile'dde'scription,

In the drawings,

. suhstantially to'be'mo. nted tponthe inai'tin inf; ad splaite notnshown) .uponwhich'theit on e vehiclewhose front w e is meafsul d Iisiib;

ported. handled is'mountednponithe standard I for the convenient manipulation fp'f the s an I v n The upper end of the vertical' arrnj 2 ofth'e standard l carries. abio'ck't' inwhich' a rodf'fi of. squarev cross-section throughout, the major ;por tion oi its length is slidahly positionedl Abortion l of the rod6 is jzof round crossesection whereby by moving said rodto its extreme left-position, as viewed in 1, said rodn'iay be-rotated within the blqckfe. 'i i-ovvever j jdin ing the measurement operation, as'ffwill hereinafter be described; and rod-t "is hon-rotatably positi ned within block a knob sisters -at -the"end o"f the rod 6 functions as see hien-t cans forrnanipulating- Sam i I I I l At the opposite end of the supporting rod 6; a

the invention resides in the his. 1 is a side eievational view, ofjmy wheel control mechanism 9 is mounted; The fnee'ha l a 2,603,881w i I Y WHEEL ALIGNMENT-GAUGE .n 'Harold Q; Hola.day,,R0ck lament, a s sh rt "Bearflvlanufacturing -'Cornpany, Rock"Island; I "Lil a-corporation Delaware afitagabitifitro, 1947f, serial as 749,141 r Qll irn'sfmiss-463.15) Y 2 I I V bracket 42 which ,in turn,is provided with a pair .of clips. 13 adapted to carry a square-sectioned rod or gauge bar M. The rod or gaugebar M carries a wheel arm 15 adjacent each end thereof,

each of said wheel arms being provided with a sleeve 18, which has a square-sectioned opening conformable withtheibar i4 and which is Slid', able upon said bar. .A set screw 1 I is threadedly positioned in each sleeve .16 and functions to lock each l wheel arm "15in ,afldesired position along the length or the rod l4. Referring particularly to Fig. 3, the control mechanism 9 comprisesa U-shaped bracket [3, which is rigidly mounted upon theendcportion of the-slidabie bar 6, being secured thereto by means ofiock nuts 9 which .are threadedlyengaged upon the. bar Eon each side of the bracket 18. a A im' ar U-shaped.,-hiiacket '220- is pivotalli moiintednponthehracket 18 ,v A'rmZi of bracket 2G is provided with-an enlarged "aperture in which the enlargedlshahk of, a screw,.22 .is loosely positioned. The adjacent arm 23,0f the bracket is aisoiaperturefli throughout a I portion of its thick.- ness in receivetheenlarged portion of the screw Z21 ,Th elend of the screw 22 is of restricted diameter asshown best at 25 in Fig. 3, the restricted portion being threaded tolreceive nut25. The arrangement is suchthat the screw 22 is mounted rigidly upon arm 2,3 of the braeketi fi and the arm 2| of bracket 20 can rotate relative thereto about the enlargedfportionof the screw 22, a

Arm 2,5 of'bracket 25 is similarly apertured to receive the .enlargedishank of a screw 2? which is loosely positioned'with respect'to said arm. Arm .28 of, bracket lBfisalso a'pertured throughout. a portion of itsthifiknss to conform with the enlarged portion of theshank ofgscrew 2.1. The remaining portion .of the screw i2? is of restricted diameter and is provided with external threads 29. 'upon which lock nut 39 is engageable. The arrangement is such that the screw 21 may be held rigid upon arm 28 by means of the lock nut 33. Y I

.,';As has been 'hereinbefore described, the bar 14 is,ri'gi;d'With reSpcCt tO the disk H. externaily' and internallythreaded sleeve is rigidly secured'to the disk I I and passes ioosely through apertuies (not showny'provided in disk In and bracketfifl. "A nut 32 threadedly engages the exterior ofs1ee've"3-| and frictionally jhol'ds disk H, disk wand bracket 20 in asSembledrelatiom ship, permitting, however, relative --slid'able mov rotary fashion." I f I A variable resistance unit 33 is mounted upon I one arm 34 of an angle shaped supper-V35, the

opposite arm 36 of said support 'bei-ng' 'securedi tob racket 20 bymeans of a screw or the like 31. v

The resistance unit 33 carries an externally threaded sleeve 38 which passes loosely through an aperture {not shown) in arm 34, and anu-t 39 merit of disk I l}! with respect to disk- "tin =afunctions to lock said sleeve rigidly upon the arm 34, thereby rigidly securing the resistance unit 33 upon the arm34.

The variable resistance 33 is of the usual dial type having a rotatable contact arm (not shown) which changes the value of the resistance in accordance with the angular displacement of the variable resistance 62 corresponds to the resistcontact arm. A screw 40 is mounted upon the end of the rotatable contact-arm, s'aid screw, 1O

loosely projecting through the sleeve 38. The external portion of the screw 40 is threaded and is threadedly engageable with interior screw threads carried by the screw 21, and a lock nut 4| is threadedly mounted upon the exterior of the screw 48 whereby the screw 49 and the screw 21 are secured together as a unit.

.It can readily be seen that inasmuch as the screw 40 is rigid with respect to the bracket l8, and that the resistance unit 33 is rigidly 'posi- 1 tioned with respect to the bracketi28, rotation of the bracket 26 about the screws 22 and 21, causes relative rotation of the screw 40 with respect to the resistance unit 33. In this manner the contact arm of the resistance unit is angularly displaced in proportion to the angular displacement of bracket 20 with respect to bracket I 8. v

A'similar variable resistance unit 42 is rigidly mounted upon a support 43 which in turn is rigidly secured to bracket 20 by means of screw 6 44. The contact arm (not shown) of the variable resistance unit 42 is mounted upon screw 45, and a lock .nut 46 threadedly engages the external threads of the screw 45 to securely position the resistance unit 42 upon thesupport 43.

The arrangement is such that when disk ll isrotated with respect to disk I0, there is an angular displacement of the contact arm of the variable resistance 42 with respect to the resistance unit thereof. In view of the fact that the bar I4 is rigidly mounted withrespect to the disk H, the angular displacement of the'bar I4 is proportional to the amount of resistance thrown into or taken out of the circuit in which the unit 42 is connected.

Referring particularly to Fig. 4, the electrical circuit employed in my invention is illustrated schematically. In this circuit a battery 41 is connected through switch .48 .to a variable resist ance 49.5 The opposite end of the variable resistance 49 is connected to an arm 50 which includes a fixed resistance The same end of the variable resistance 49 is also connected to arm '52 which includes a fixed resistance 53, A galvais connected through variable resistance 64 to the P915015 h b y 41 which is common to the Conductor-55.-

A'control cabinet 65 is supported upon the member 5iand carries a sloping panel 66 upon which is mounted meter 54' corresponding to galvanometer 54, which isprovided with two calibratedrd-ialst 61 and 68. A control-knob64' ance contained within the resistance unit 42.

It will be noted that the resistances together with. the meter 54 and source of E. M. F. 4'! are connected in the form of the usual resistance bridge ofthe'Wheatstone type wherein resistance53 is contained in one arm; resistance 5| is contained in another arm; resistance 64 is containedin a third arm; and, resistances 58, 68 or 62, selectively, are contained in the remaining arm. Resistance 49 is a control resistance which regulates the voltage applied to the bridge. Resistance 68 is 'a balancing resistance and is normally set to balance the bridge when connected into circuit whereby no current will flow through the meter 54. Resistances 49 and are contained within cabinet 65 and are preset and are not varied during the making ofthe tests.

In adjusting the device, with the bar I 4 dis posed at right angles to the rod 6 and with the bar l4 in a vertical position, resistance 68 is connected into circuit by means of the selector switch 56. Resistances 64 and 68 are adjusted to obtain a zero reading uponthe meter 54.

With the bar l4 in this position a balanced read by the screws 40 and 45 respectively produces proportional changes in the resistances, and scales 61 and 68 are calibrated to interpolate these changes in resistances through the change of current in meter 54 in terms of degrees of angular displacement of caster, camber, king pin inclination and toe in.

To utilize the present inv'ention to ,measure camber of the front wheels of an automobile, the front wheels of the vehicle are placed-upon opposite turning radius plates. A gauge, as here inbefore described, is mounted upon each of .the turning'radius plates and with the bar 14 of one of the gauges disposed vertically the support 6 is moved inwardly toward a front wheel and the arms [5 are adjusted so that the ends thereof contact the rim of the wheel. The selector switch, after switch 48 has been closed, is moved to its camber position, that is, resistance 58 of resistance unit 33 is placed in circuit. Bracket 28 will then be displaced about bracket "3 and, hence, the resistance within 33 (resistance 58) will be varied and, hence, the bridge will become unbalanced. to adegree indicated upon meter; 54 as interpolated by scale 68. In-view of the fact that the bar I4 has been displaced-from its nor mal or preset position, the displacement willbe measured by virtue of the variation of the resistance 58 from its bridge-balancing position. I-Ience,theamount of camber, in degrees, can be 7 read directly from scale 68.

To measure caster, the brakes of the vehicle are locked and the frontwheel to be measured is turned toward the longitudinal center line of the vehicle through an angle of twenty degrees.

'With the bar M in its vertical position and the selector switch set to its "caster position, that is with resistance 58 (resistance unit 33) in circuit, the support 6 is moved inwardly toward the wheel and the wheel arms l are brought into contact with the rim of the wheel. The needle of the meter will be displaced by virtue of the canting movement of the bar 14. The knob 64 is then manipulated until the needle is returned to its zero position upon dial 61.

The support 6 is then moved rearwardly and front wheel being measured of the vehicle is turned outwardly from the longitudinal center line of the vehicle through an arc of twenty degrees. The support 6 is then again moved inwardly until the wheel arms l5 contact the wheel rim. The caster angle can then be read directly from scale 61.

To measure king pin angle, the brakes of the vehicle are locked and the front wheel to be measured is turned toward the longitudinal center line of the vehicle through an angle of twentyfive degrees. With the bar I4 in its vertical position and the selector switch set to its "king pin position, that is with resistance 62 (resistance unit 42) in circuit, the support 6 is moved inwardly toward the wheel and the wheel arms l5 are brought into contact with the rim of the wheel. An index mark is placed upon the wheel rim where the wheel arms contacted said rim.

The support 6 is then moved rearwardly and the front wheel being measured on the vehicle is turned outwardly from the longitudinal center line of the vehicle through an arc of twenty-five degrees. The support 6 is then moved inwardly until the wheel arms l5 contact the wheel rim, the bar l4 being rotated to bring the arms in registration with the index marks previously placed upon the rim. The king pin inclination can be read directly from scale 68.

To measure toe-in, the support 6 is moved rearwardly until said support can be rotated. The support is then rotated until bar [4 is brought to a horizontal position and. the support is then moved forwardly until the wheel arms [5 contact the rim of the front wheel. The knob 56 is turned to the toe-in position, that is resistance 58 (resistance unit 33) is in circuit. At this position the meter 54 will show a reading other than zero if the wheel has any degree of toe-in. The wheel is then moved from its original position until the meter shows a balanced condition of the circuit, that is, the meter reads zero. The gauge on the opposite side of the vehicle is then used. With the bar I4 of said gauge in a horizontal position, the knob 56' is moved to "toe-in position, that is resistance 53 (resistance unit 33) is placed in circuit. The support 6 is then moved forwardly until wheel arms I5 contact the wheel rim and toe-in is indicated in inches upon scale 68.

It is to be understood that broadly my invention is directed to a device for electrically indicating and measuring the alignment angles of the wheels of an automotive vehicle and for purposes of illustration a resistance bridge circuit is shown. However, the specific bridge circuit is not, per se, my invention and any of the usual bridge circuits can be employed where the variation in impedance caused by angular displacement of a variable impedance is interpolated by a current measuring device in terms of angular measure.

-By impedance as used in the specification and claims is meant resistance, inductance or capacitance or combinations thereof, depending upon the particular type of bridge circuit and electric current employed.

I claim as my invention:

1. An automotive wheel alignment gauge comprising in combination, a standard adapted for movement toward and away from an automobile wheel, a support movably carried by said standard, a bracket carried upon said support, a second bracket pivotally-mounted upon said first mentioned bracket, 2. gauge bar carried upon said second bracket for contacting spaced portions of the rim of a wheel when said support is moved relative to said standard, a resistance unit comprising two members rotatable relative to each other to change the resistance thereof in proportion to the rotatable displacement of the two members, one of said members being mounted upon said first bracket and one of said members being mounted upon said second bracket, a resistance bridge circuit, the resistance of said resistance unit being connected in one arm of said bridge circuit and balancing resistances connected in the remaining arms, a current measuring meter connected across said bridge, and calibrations on said meter for interpreting change in current caused by change in said first mentioned resistance in terms of angular displacement of said brackets relative to each other.

2. An automotive wheel alignment gauge comprising in combination, a standard, a support movably carried by said standard, a bracket mounted upon said support, a gauge bar, rotatable means for mounting said gauge bar upon said bracket, said gauge bar being adapted to contact the rim of a Wheel at spaced portions thereof when said support is moved relative to said standard, a variable resistance unit comprising two members rotatable relative to each other to change the resistance of the resistance unit in proportion to the rotatable displacement of the two members, one of said members being mounted upon said bracket and the other member being connected to said rotatable means and being movable with said bar, a resistance bridge circuit, the resistance of said resistance unit being connected in one arm of said bridge circuit and balancing resistances being connected in the other arms of said bridge, a current responsive meter connected across said bridge, and calibrations on said meter for interpreting change in current caused by change in said first mentioned resistance in terms of angular displacement of said gauge bar relative to said bracket, and means for independently varying the resistance of one of the balancing resistances of said bridge.

HAROLD O. HOLADAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,859,222 Rogers May 17, 1932 2,036,458 Carlson Apr. 7, 1936 2,061,326 Morse et a1 Nov. 17, 1936 2,198,523 Adams Apr. 23, 1940 2,210,970 Bonell 'Aug. 13, 1940 2,346,360 Creagmile Apr. 11, 1944 2,437,639 Floyd Mar. 9, 1948 FOREIGN PATENTS Number Country Date 62,650 Norway July 1, 1940 

